Patent GB-840031-A (GB)
Title: Improved machine for severing continuous lengths of materials into separate pieces
IPC: D06H7/02
Filed: 1955-07-02
Abstract: 840,031. Photo-electric control systems. SJOSTROM, R. L. July 2, 1956 [July 2, 1955], No. 19196/55. Class 40 (3). [Also in Groups VIII, XVI and XXXVIII] A machine for severing individual pieces from a continuous length of material having transverse bands of different qualities comprises tracking means utilizing the bands as a guide and a cutting mechanism adapted to sever the pieces transversely, the instantaneous longitudinal position of the cutting mechanism during cutting being controlled by the tracking means. In the embodiment towels are cut from a continuous length of fabric having dividing bands more opaque than the main portions and a photo-cell senses a selected band edge after the automatic feed to the cutter of a predetermined length and its response guides the cutter longitudinally. After its leading edge has been cut and removed by an air doffer towelling 91, Fig. 3, with transverse bands such as 92 is pulled longitudinally by clamps 65 on carriage 58 the clamps opening as they pass over table 3, closing over the leading edge of section 91 and withdrawing a predetermined length to bring the next transverse band over glass plate 4 for cutting by tool 21 on support 18. Cutting tool carriage 8 is reciprocated over the table by parallel chain conveyers 30, 31 in synchronism with the longitudinal reception of carriage 58 so that the cutting carriage returns from its cutting stroke with the tool raised as feeding over the table takes place. Carriage 8 supports a photocell receiving light emanating from transverse fluorescent lamps under the glass plate, Fig. 1 (not shown). During the cutting traverse tool 21 is controlled longitudinally by lead screw 15 to cut along the centre line of the transverse band. Longitudinal control of cutting tool, Figs. 8, 11.-During the cutting traverse photo-cell 26, Fig. 8, acting through adjustably biased amplifier 151 and amplifier 153 causes relay contacts 156 to selectively close a circuit to one or other magnetic clutch 13, 14, Fig. 3, of contra-rotating motors 11, 12 over-running of the lead screw being avoided by microswitches 28, 29 connected in series with respective clutch coils. Alternatively photo-cell 26, Fig. 11, is connected in a bridge circuit 159 fed with a unidirectional pulsating voltage and whose output via comparator 160 and amplifier 162 triggers the thyratron 163 or 164 whose grid input is in phase with its A.C. anode supply voltage fed in series with the appropriate clutch coil. In a modification a single two-phase motor is controlled to drive the lead screw, Fig. 12 (not shown), or a single reversible D.C. motor is used and connected in the cathode circuits of the thyratrons so that the motor is de-energized before a zero photo-cell alignment error and hunting is minimized, Fig. 13 (not shown). Feeding material, Fig. 3.-The lagging edge of the cut piece is doffed by air from a perforated tube above and parallel with glass plate 4 the air valve being opened by a microswitch actu- . ated during the non-cutting traverse of carriage 8. Clamps 65 close over the leading edge of material 91 and draw it forward as carriage 8 moves along its return stroke, the clamps opening at a predetermined point determined by an adjustably - positioned microswitch so as to locate the transverse band in its theoretically correct position on plate 4 for cutting. Each clamp comprises an upper jaw fixed to a transverse shaft and a lower jaw to which is secured leaf springs the lower one 70 engaging the upper surface of table 3 to ensure that the towelling to be gripped is carried above the lower jaw, Fig. 5 (not shown). At intervals corresponding to e.g. fifty towels an additional photo-cell detects the lagging edge of the thick section being fed and causes clamps 65 to open, Fig. 16 (not shown). Cutting material, Fig. 3.-After feeding the towelling is clamped by normally open members 53 and a similar oppositely disposed pair, Fig. 1 (not shown), the clamp jaws being closed by solenoids immediately prior to cutting and acting to hold down the material and draw it outwardly to stretch and straighten it, Fig. 14 (not shown). Cutting tool 21 comprises a motor 22 driving a blade protected by an apron, Fig. 2 (not shown) ; sharpening implements secured to support 18 may be provided, Fig. 4 (not shown). The blade is a predetermined and adjustable longitudinal distance from the photocell so that the transverse dividing band is bisected. In its movement carriage 8 encounters spaced microswitches which (1) cause reversal of the conveyer's driving motor when the carriage nears an end of a traverse, (2) energize the circuit of the magnetic clutches after a brief interval during which the photo-cell hunts longitudinally to find the selected transverse band edge, and (3) subsequently de-energize the clutch circuit to avoid longitudinal cutter movement as the photo-cell enters the unobstructed light through the glass plate, ahead of the cutting blade, Figs. 1, 10 (neither shown). During the non-cutting traverse of carriage 8 finger 44 is carried upwards by a runner into a guide channel 43 to lift the cutting blade clear as the next section of material is pulled forward, Figs. 2, 4 (neither shown).